Process of tanning.



UNITED STATES PATENT OFFICE.

CHARLES S. DOLLEY, OF PHILADELPHIA, PENNSYLVANIA.

PROCESS OF TANNING.

SPECIFICATION formingpart of Letters Patent No. 630,494. dated August 8, 1899.

7 Application filed October 21, 1896. Serial No. 609,600: (No specimens-l T0 aZZ whom it may concern.-

Beit known that 1, CHARLES S. DOLLEY, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Tanning; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to improvements in tanning hides or skins; and the objects of the invention are to provide a single-step tanning process which is simple, inexpensive, efficient, and rapid, and to produce a soft, tough, and pliable leather sound in'texture and which is free from discoloration and harmful foreign matters and is Well adapted to be finished and colored by any of the ordinary finishing and coloring methods and agents.

My invention consists, essentially, in subjecting the hide or skin to be tanned to the action of formic aldehyd (011 0) in such manner and proportion and for such time that the hide or skin under treatment shall be thoroughly permeated by the formic aldehyd, which I have discovered will under proper conditions form an insoluble compound-with the gelatinous constituents of the hide or skin and at the same time effect those other chemical and physical changes essential to the conversion of a raw hide or skin into leather.

In carrying out my process I take a hide or skin which has been prepared for tanning by one of the commonly-employed modes, according to the particular character of the hide or skin under treatment, and I subject said prepared hide or skin to the action of formic aldehyd either in its natural gaseous condition or in aqueous solution, the degree of concentration of the gas or the strength of the solution and the time of treatment varying, of course, with the character and thickness of the hide or skin to be tanned.

If the formic aldehyd be employed in the I form of an aqueous solution, I have found the following an advantageous method to pursue for the conversion of ordinary goat-skins into Morocco leather: I begin the treatment with preferably, say, a three-per-cent. solution of the formic aldehyd and treat the skins in this solution in a closed drum for, say, ten minutes, adding formic aldehyd to the solution at intervals of, say, ten minutes until at the end of an hour, or thereabout, the solution has been brought up to a strength of ten per cent. and the hides have thus in the interval been subjected to the continuous action of a tannage solution of gradually-increasing strength. I have found in practice that ordinary goat-skins treated as above described may be thoroughly tanned in a period of an hour, or thereabout.

The hides or skins should be subjected to the ordinary tests known to tanners from time to time during the process and should be allowed to remain and to be agitated or revolved in the drum until said tests applied to the thickest portions of the thickest hides or. skins under treatment indicate to a person skilled in the art thorough permeation and through and through conversion of the hide into leather, the hide or skin having lost the tripy translucent appearance and peculiar feel of a raw hide and become opaque and colorless and leathery to the touch through and through.

If the formic aldehyd be used in a gaseous state, I suspend the hides or skins to be tanned in a chamber capable of being hermetically closed and connected with any suitable form of apparatus for gene-rating formic-aldehyd gas. The skins being suspended within this chamberand the door'closed, the formic-aldehyd gas is introduced into the chamber, and this is continued and the hides or skins subjected to the action of the gases or mixed gas and vapor, until the ordinary tests indicate 'to a person skilled in the art that the hides or skins have been thoroughly permeated by the tanning agent and that the conversion of the hide or skin into leather is complete. I

If the formic aldehyd be employed in a gaseous state, I find that as many ordinary prepared goat-skins in a moist condition as can be suspended in a tight chamber having 2. ca

pacity of, say, two thousand cubic feet may be thoroughly tanned within a period of from six to ten hours by the action of the quantity of formic-aldehyd gas generated by the ordinary prooess from one liter of wood-alcohol.

' aqueous oral'coholic solution, andl'find that if it be used in this manner it is desirable to add a proportion of chlorid of calcium to the formic-aldehyd solution, polymerization of the formic aldehyd' being in this manner largely prevented. For this pu rpose two hundred parts of chlorid of calcium for each fi f teen hundred parts of formic-aldehyd 'solution suifices. In case the gas is employed in connection with aqueous vapor it should of course be u'nde'rstood'that live or heated steam is not employed, but rather a cool apor or moisture-charged atmosphere.

It sometimes occurs that a batch of skins wh y a j h h i nl l'ihit l thisil nss 9r oth otherc hh ma re h h hetan so i 'd 'ffr' s emi H that employed in tanning" ordinary hf'id esi o'r skins, and'it'is at once evident that i'n's'uch 4$? vthe ta ihfi m y ea i y; h 'fit h i 'h fair specimen of the batch of skins anne nd using the am a h t stfq r th trhh th f h hh s s ht t quired we reaailydaerm ie he st hhs hh us solution which may be required in 'tal 'niq'g such hidesor skins.

lunde ah athe e hn a y speakin fh he p cul ar p od t resul n fr m he action, o a ann ng en upon he l o eh and connective tissue "constituents of animal hideor skin, which'product is characterized h st n uish d 'Q l w k by l h m'tcal peculiarities varying with the special tanning sen employed in all ase Jb e fa t h .9 nn ns nt has ent red htfl tcombination with the skin substances andi's 1 tween formic aldehyd and the collogen and connective tissue of animal skin, and'as 'a new article or manufacture is tobe"distinguished from other leatherssucl1 as oak, hemlock, or chrome leather-by any or all of the following tests: first, by coming from the tannin at ree'froth any siisapl rh i due to the tanning agent; second, by its freedom from material depositssuch as the pigment, Poss, resin, am, deposited in the skin in barktannageor from the product of the reduction of mineral salts, as in mineral tannage, and, 'thiid,'"by any or all of 'the'varioiis tests for formic aldehyd, inasmuch as a certain amount of this substan'ce'when used as a tanhing g m ns in a u comhin t tate in he sk n, n'w'h'i'th'i m' yh dtbt gl- H 'vih' t deh r hhd' hj ihvhn itn; Wha I cla m e h m hti d is rl stt th y I s -1t A th w article of .m anu acturmanned ide o skin; .c'bh ti geh eht ytt h ioihhi tt h' Qt o hl h d with he tQ in nd Q'th r eht h ul Qhs i hhh S'Qf he. Sai hide or skin, substantially'as herein set forth.

2; As a new article of manufacture, leather obtained by treating animal hide or skin with fum aldieh fi hhr by rentls s u uuue and non putrescible' the ilubgli or connectnot to be recovered, as arethe salt and alum se n w s he h th fas 'th 'cer ain phy i tl er o' s are pr'tzd ih i jshch, o

example, as being insoluble andnd -pnnies ble and by d ffo e c n densityg'e as ib y, h rma i y o igh and ma familiar to pastas ski d in ann ng: matters iif ir u h 'h siifierent ehtfs a differen hemih l c aiht s, o h pos ss h' a ma a h si resmbla hh hus the 'ssta'no T at h ich; fit erng to c t t h' ha ies (Watt'page 3 ,40 hdhped' by o thh t aeittbhins a d fi re sh A. s fromthe chromatized ge auntr thechrome pr ce s- My' leat e is i i e r m sk t Loy hifil b r 'hsthhihs a htiht t hhmh ht t h htt- T n 'ocessher n es nhed f ann hat s 9 say; s'hh t h f hef hide 'Qr' ki heta' hs Jto the ac io f mi h qe 'y 15 mm hh h w h aqu uhs vapotsii h hh l its h n tht hrth The process of tanning, which consists in s jh ih the h hr nt b tanned; 0 he T c l of f9? v mo'i tl in l tzl t jh S S an tt1lyset1 9 1. In eStimQhY wh eof fifi mysig a', 1" inpreserice of two witnesses.

CHARLES s. DOLLEY.

i au ywrtui t W tnesses A'S- Q- MQR QN, H- B ti-P'QF- 

